[Synthetic pyrethroid insecticides and development of resistance to them]

After the structures of pyrethrins, the insecticidal components of pyrethrum flowers, were determined, syntheses of derivatives of them were undertaken, and first generation synthetic pyrethroids, such as allethrin, resmethrin and phenothrin, were produced. Due to lack of photostability in these compounds, their use was limited to the control of sanitary or household pests. The syntheses of second generation synthetic pyrethroids, i.e., permethrin and fenvalerate, overcame a lack of photostability. These are now widely employed in the areas of agriculture and public health. Development of resistance in insect pests is the only difficulty to the future success of ideal insecticides, or synthetic pyrethroides. In this review, information regarding the development of pyrethroid resistance is summerized, and also the importance of nerve insensitivity to the chemicals, as a mechanism of resistance in insects pests, is pointed out.